Flowmeter

Abstract

Provided is a flowmeter comprising: a flow path formation member forming an internal flow path through which a fluid flows; a fluid resistance element that has a columnar shape composed of a ceramic material and that includes a resistance flow path fixed to the internal flow path; a pressure sensor that detects pressure applied to the fluid resistance element on an upstream side or a downstream side; and a seal member interposed between the fluid resistance element and a wall surface of the internal flow path, wherein the fluid resistance element includes a tapered surface formed at an end portion thereof in the axial direction, and the tapered surface is fixed in contact with the seal member.

Description

flow meter

[0001] This invention relates to a flow meter.

[0002] Conventionally, flow meters are known that measure fluid flow rate based on the upstream and downstream pressures when fluid is flowed through a fluid resistance element, which has a flow path that provides resistance to the flow of fluid (hereinafter also referred to as a resistance flow path).

[0003] Incidentally, in flow control devices for material gases used in semiconductor manufacturing, for example, the fluid resistance elements used therein need to be extremely fine in order to achieve the required flow control accuracy, and sometimes a resistance channel with a thickness of several tens of micrometers is required.

[0004] As shown in Patent Document 1, if a fluid resistance element is made of ceramic, it can be processed with high dimensional accuracy, making it possible to stably manufacture fluid resistance elements with uniform resistance characteristics. However, when trying to fit a ceramic fluid resistance element with the same diameter into a very narrow channel of a few millimeters in diameter, such as when controlling a low-flow fluid, the fluid resistance element may break or get damaged, making it difficult to incorporate into a fluid control device.

[0005] Patent Document 2 describes a fluid control device that incorporates a fluid resistance element by covering the outer surface of a ceramic channel forming member with a metal covering member. This allows the device to enjoy the advantages of forming a resistance channel using ceramic while being easily incorporated into a fluid flow channel.

[0006] Japanese Utility Model Publication No. 59-77027, International Publication No. WO2021 / 095492

[0007] Incidentally, in recent years, the use of corrosive fluids in semiconductor manufacturing processes has been increasing. In the fluid resistance element described in Patent Document 2, a metal material is used in part of the wetted portion of the fluid resistance element. Therefore, if a corrosive fluid is flowed through it, corrosion may occur, leading to contamination and potentially adversely affecting the manufacturing process.

[0008] This invention has been made in view of these problems, and its main objective is to provide a flow meter having a fluid resistance element that can be easily incorporated into a fluid flow path while enjoying the advantages of forming a resistance channel using ceramics, and furthermore, does not cause contamination even when corrosive fluids are flowed through it.

[0009] In other words, the flow meter of the present invention measures the flow rate of a fluid based on the upstream or downstream pressure applied to a fluid resistance element provided in an internal flow path through which the fluid flows, and comprises a flow path forming member that forms the internal flow path, a columnar fluid resistance element made of a ceramic material having a resistance channel fixed to the internal flow path, and a sealing member interposed between the wall surface of the internal flow path and the fluid resistance element, wherein the fluid resistance element has a tapered surface formed at its axial end, and the tapered surface is in contact with and fixed to the sealing member.

[0010] With this design, the fluid resistance element is made of ceramic material, allowing for high dimensional accuracy during processing and enabling the stable production of fluid resistance elements with uniform resistance characteristics. Furthermore, since the entire fluid resistance element can be constructed from corrosion-resistant ceramic material, contamination due to corrosion does not occur even when corrosive fluids are flowed through it. This allows for the measurement of fluid flow rates without adverse effects in semiconductor manufacturing processes that use corrosive fluids.

[0011] Furthermore, since the fluid resistance element is fixed to the internal flow path via a sealing member, there is no need to worry about liquid tightness between the side surface of the fluid resistance element and the inner wall surface of the internal flow path into which it is inserted. This allows the outer diameter of the fluid resistance element to be designed to be smaller than the flow path diameter of the internal flow path. As a result, the contact resistance of the fluid resistance element when it is incorporated into the internal flow path is reduced, preventing the risk of damage.

[0012] Furthermore, since the tapered surface formed at the axial end of the fluid resistance element is in contact with the sealing member, the force applied to the fluid resistance element can be distributed in both the axial and radial directions through contact with the sealing member, further reducing the risk of damage when incorporated into the internal flow path.

[0013] In the flow meter, it is preferable that the flow path forming member is made of a ceramic material. In this way, the entire flow path through which the fluid passes in the flow meter can be made of a ceramic material, further reducing contamination due to corrosion. Compared to when it is incorporated into an internal flow path made of a metal material, when a fluid resistance element made of a ceramic material is incorporated into an internal flow path made of a ceramic material, the risk of damage to the fluid resistance element is higher. However, as described above, in the present invention, by making the tapered surface formed at the axial end of the fluid resistance element contact the sealing member, it can be incorporated into the internal flow path without difficulty.

[0014] Furthermore, a specific embodiment of the flow meter is one in which the flow path forming member comprises a plurality of flow path forming blocks that are separable from one another, and the housing space in which the fluid resistance element is housed in the internal flow path is divided and formed by the plurality of flow path forming blocks. In this way, contact resistance when incorporating the fluid resistance element into the internal flow path can be reduced, and the risk of damage can be further reduced. In addition, the fluid resistance element can be easily removed from the internal flow path.

[0015] Furthermore, a specific embodiment of the flow meter is one in which the flow path forming member comprises, as the plurality of flow path forming blocks, an upstream block that forms the upstream region in the containment space and a downstream block that forms the downstream region in the containment space, and the fluid resistance element is fixed by being sandwiched between the upstream block and the downstream block from both sides along the axial direction. In this way, the fluid resistance element can be fixed in the containment space by being sandwiched between sealing members from both the upstream and downstream sides.

[0016] An embodiment in which the effect of the present invention is remarkably exhibited includes one in which the fluid resistance element is formed of silicon carbide. By forming the fluid resistance element from silicon carbide, contamination does not occur even when an acidic or basic fluid (for example, acetic acid) is flowed as a corrosive fluid. In addition, since a fluid resistance element formed of silicon carbide is more easily broken than a fluid resistance element formed of another ceramic material such as alumina, the effect of the present invention becomes more remarkable.

[0017] In addition, when there is only one resistance flow path formed in the fluid resistance element, it is necessary to lengthen the fluid resistance element to generate a differential pressure between the upstream and downstream sides, which increases the risk of breakage during incorporation into the internal flow path. Therefore, the effect of the present invention is more remarkably exhibited in such a case where the fluid resistance element has one resistance flow path penetrating in the axial direction.

[0018] In the flowmeter, it is preferable that a space layer is formed between the side peripheral surface of the fluid resistance element and the wall surface of the internal flow path. According to this configuration, the chance of contact of the fluid resistance element during incorporation into the internal flow path can be reduced, and the risk of breakage can be reduced. Furthermore, by forming the space layer between the side peripheral surface of the fluid resistance element and the wall surface of the internal flow path, the thermal influence from the outside on the fluid resistance element can be reduced, and measurement accuracy can be improved.

[0019] The fluid control device of the present invention is characterized by comprising: the flowmeter of the present invention described above; a fluid control valve; and a valve controller that controls an opening degree of the fluid control valve based on a deviation between a set flow rate and a flow rate of a fluid to be measured output by the flowmeter. With such a fluid control device, the same operational effects as those of the flowmeter of the present invention can be obtained.

[0020] According to the present invention, it is possible to provide a flowmeter having a fluid resistance element that can be smoothly incorporated into a fluid flow path while enjoying the benefits of forming a resistance flow path using ceramic, and that does not cause contamination even when a corrosive fluid flows therethrough.

[0021] A perspective view schematically showing the overall configuration of a flowmeter according to an embodiment of the present invention. A cross-sectional view schematically showing the configuration of the flowmeter according to the embodiment. A perspective view showing the configurations of a fluid resistance element and a seal member according to the embodiment. A cross-sectional view schematically showing the configuration of the flowmeter according to the embodiment. A diagram explaining a method for fixing a fluid resistance element of the flowmeter according to the embodiment. A cross-sectional view schematically showing the configuration of a flowmeter according to another embodiment.

[0022] Hereinafter, an embodiment of the flowmeter 100 of the present invention will be described with reference to the drawings.

[0023] The flowmeter 100 of the present embodiment is used, for example, in semiconductor manufacturing processes. It is a pressure-type flowmeter in which a fluid resistance element 4 is provided in a flow path through which a fluid flows, and the flow rate is measured by detecting the upstream pressure and the downstream pressure of the fluid resistance element 4 respectively.

[0024] Specifically, as shown in FIG. 1 and FIG. 2, this flowmeter 100 includes: a flow path forming member 1 that forms an internal flow path R through which a liquid such as a liquid for semiconductor processes flows; a fluid resistance element 4 provided midway along the internal flow path R; an upstream pressure sensor 2 provided on the flow path forming member 1 for detecting the upstream pressure applied to the fluid resistance element 4; a downstream pressure sensor 3 for detecting the downstream pressure applied to the fluid resistance element 4; and an information processing unit (not shown) that calculates the flow rate of the fluid flowing through the internal flow path R based on the pressures detected by the upstream pressure sensor 2 and the downstream pressure sensor 3.

[0025] The flow path forming member 1 is a block-shaped member having a rectangular parallelepiped shape penetrated by the internal flow path R, and is entirely made of a ceramic material (specifically, silicon carbide). A seal member 12 is provided interposed between the wall surface of the internal flow path R and the fluid resistance element 4. An external inflow pipe H is provided at one upstream end of the flow path forming member 1 １ is connected, and an external outflow pipe H is provided at one downstream end ２ is connected.

[0026] The upstream pressure sensor 2 is located upstream of the fluid resistance element 4, and the downstream pressure sensor 3 is located downstream of the fluid resistance element 4. The upstream pressure sensor 2 is attached to the flow path forming member 1 so as to cover the openings of the upstream inlet passage R11 and the upstream outlet passage R12 formed in the flow path forming member 1. The downstream pressure sensor 3 is attached to the flow path forming member 1 so as to cover the openings of the downstream inlet passage R13 and the downstream outlet passage R14 formed in the flow path forming member 1. The upstream inlet passage R11, the upstream outlet passage R12, the downstream inlet passage R13, and the downstream outlet passage R14 are all formed to open on one surface of the flow path forming member 1 in the vicinity of the fluid resistance element 4 in the internal flow path R. The upstream pressure sensor 2 and the downstream pressure sensor 3 are driven by a sensor drive circuit (not shown), and the detection signals indicating capacitance obtained by each sensor 2 and 3 are amplified by an amplification circuit (not shown) and converted into flow rate by a calculation circuit (not shown). Each of the sensors 2 and 3 is not limited to capacitive types; for example, they may be strain gauge types equipped with a diaphragm strain gauge, or piezoelectric types (piezoelectric type) equipped with a piezoelectric element on the diaphragm.

[0027] The information processing unit is a general-purpose or dedicated computer equipped with a CPU, memory, input / output interface, AD converter, etc. This information processing unit, by coordinating the CPU, peripheral devices, etc. according to a predetermined program stored in a predetermined area of ​​memory, performs at least the functions of a storage unit that stores flow characteristic data showing the flow characteristics of the fluid resistance element 4, and a flow calculation unit that calculates the flow rate based on the measured values ​​received from pressure sensors 2 and 3 and the flow characteristic data. The flow characteristics of the fluid resistance element 4 shown by the flow characteristic data indicate the relationship between the upstream pressure applied to the fluid resistance element 4, the downstream pressure applied to the fluid resistance element 4, and the flow rate of the fluid passing through the fluid resistance element 4.

[0028] In the internal flow path R, an accommodation space S for accommodating the fluid resistance element 4 is formed between the upstream-side lead-out path R12 and the downstream-side lead-in path R13. This accommodation space S is a region whose inner diameter is partially enlarged in the linear internal flow path R connecting the upstream-side lead-out path R12 and the downstream-side lead-in path R13. This accommodation space S is a columnar region having a constant cross-sectional shape (circular shape) along the flow direction. The upstream end of the accommodation space S is concentrically connected to the linear introduction flow path R15 having a smaller inner diameter, and the downstream end thereof is concentrically connected to the linear discharge flow path R16 having a smaller inner diameter. A step is formed at each boundary between the accommodation space S and the introduction flow path R15 as well as the discharge flow path R16.

[0029] The flow path forming member 1 includes a plurality of (here, two) flow path forming blocks 11 that are separable from each other along the flow direction, and is configured by aligning the plurality of flow path forming blocks 11 with each other and fixing them using a fastening mechanism (not shown). The accommodation space S is divided and formed in the plurality of flow path forming blocks 11.

[0030] Specifically, the flow path forming member 1 serves as the plurality of flow path forming blocks 11, and includes an upstream region S in the accommodation space S Ｕ form an upstream block 11 Ｕ and a downstream region S in the accommodation space S Ｌ form a downstream block 11 Ｌ and. The opposing surfaces of each flow path block are formed so as to be orthogonal to the axial direction of the accommodation space S. The fluid resistance element 4 is Ｕ and the downstream block 11 Ｌ sandwiched and fixed by. Note that the upstream block 11 Ｕ 's opposing surface and the downstream block 11 Ｌ 's opposing surface are liquid-tightly fixed using a sealing member 12 such as an O-ring (not shown).

[0031] The fluid resistance element 4 generates a pressure difference between its upstream and downstream sides. As shown in Figure 3, the fluid resistance element 4 is cylindrical in shape and is entirely made of ceramic material (specifically silicon carbide). The fluid resistance element 4 has one or more resistance channels 4r that penetrate along its axial direction. These resistance channels 4r provide resistance when the fluid flows and are linear in shape with a circular cross-section. The fluid resistance element 4 is formed such that its axial length is approximately the same as the length of the housing space S, and its outer diameter is smaller than the inner diameter of the housing space S.

[0032] A tapered surface 41 inclined with respect to the axial direction is formed on at least one end (in this case, both ends) of the fluid resistance element 4 in the axial direction. Specifically, one or both ends of the fluid resistance element 4 in the axial direction have a truncated cone shape (specifically, a frustoconical shape), and the aforementioned tapered surface 41 is formed by its side surface. That is, this tapered surface 41 is formed around the axis. The fluid resistance element 4 has a shape that is rotationally symmetric with respect to the axis.

[0033] The fluid resistance element 4 is then fixed in a liquid-tight manner within the containment space S via a sealing member 12. Specifically, sealing members 12, which are O-rings, are attached to the upstream and downstream ends within the containment space S. The outer diameter of the O-ring is approximately the same as the inner diameter of the containment space S, and it is fitted into the containment space S with its central axis aligned. That is, the upstream O-ring contacts the upstream wall surface forming the containment space S, and its outer circumferential surface contacts the inner circumferential wall surface S of the containment space S. １ It is positioned at the upstream end of the containment space S so as to be in contact with the upstream side wall surface and the inner circumferential wall surface S of the containment space S. １ Since it is compressed from above, below, left, and right by contacting the sealing member 12, the fluid resistance element 4 is positioned when it is fixed in the housing space S via the sealing member 12.

[0034] Similarly, the downstream O-ring contacts the downstream wall surface that forms the containment space S, and its outer circumferential surface contacts the inner circumferential wall surface S of the containment space S. １It is positioned at the downstream end of the containment space S so as to be in contact with the downstream side wall surface and the inner circumferential wall surface S of the containment space S. １ Since it is compressed from above, below, left, and right by contacting the sealing member 12, the fluid resistance element 4 is positioned when it is fixed in the housing space S via the sealing member 12.

[0035] The fluid resistance element 4 is fixed in the housing space S with its tapered surface 41 in contact with the sealing member 12 on both the upstream and downstream sides. That is, the tapered surfaces 41 on the upstream and downstream sides of the fluid resistance element 4 are in contact with the inner circumferential surface of the sealing member 12. In this way, as shown in Figure 4, the fluid resistance element 4 is arranged concentrically with respect to the housing space S and the sealing member 12, with the side circumferential surface 42 of the fluid resistance element 4 and the inner circumferential wall surface S of the housing space S. １ An annular space layer B is formed between them. In other words, the fluid resistance element 4 is fixed in a non-contact state with the inner wall surface of the housing space S.

[0036] In this embodiment, the fluid resistance element 4 may be configured such that its upstream end face protrudes from the housing space S. That is, the upstream end face of the fluid resistance element 4 may be located upstream of the upstream wall surface of the housing space S. Conversely, the fluid resistance element 4 may be configured such that its upstream end face fits within the housing space S. That is, the upstream end face of the fluid resistance element 4 may be located downstream of the upstream wall surface of the housing space S. The same applies to the downstream end face of the fluid resistance element 4.

[0037] The method for fixing the fluid resistance element 4 to the internal flow path R in the flow meter 100 of this embodiment will be described.

[0038] As shown in Figure 5(a), before fixing the fluid resistance element 4 into the housing space S, the upstream block 11 Ｕ Upstream region S of the containment space S formed inside Ｕ The end of and the downstream block 11 Ｌ Downstream region S of the containment space S formed inside Ｌ An O-ring sealing member 12 is pre-attached to the end. In this state, the fluid resistance element 4 is placed in the upstream block 11 Ｕ (or downstream block 11)Ｌ Insert it into the housing space S, aligning its axis with the space.

[0039] As shown in Figure 5(b), the upstream block 11 Ｕ (or downstream block 11) Ｌ When the fluid resistance element 4 is inserted all the way to the back of the housing space S, the upstream block 11 Ｕ (or downstream block 11) Ｌ The other end of the fluid resistance element 4 protrudes from the opposite surface of the downstream block 11. Ｌ (or upstream block 11) Ｕ ) are arranged so that the axis of the housing space S aligns with the axis of the fluid resistance element 4, upstream block 11 Ｕ (or downstream block 11) Ｌ ) Attach and secure it.

[0040] According to the flow meter 100 of this embodiment, since the fluid resistance element 4 is made of ceramic material, it can be processed with high dimensional accuracy, and it is possible to stably manufacture a fluid resistance element 4 with uniform resistance characteristics. Furthermore, since the entire fluid resistance element 4 can be made of corrosion-resistant ceramic material, contamination due to corrosion will not occur even when corrosive fluids are flowed through it. As a result, the fluid flow rate can be measured without adverse effects in semiconductor manufacturing processes that use corrosive fluids.

[0041] Furthermore, since the fluid resistance element 4 is fixed to the internal flow path R via the sealing member 12, the side surface 42 of the fluid resistance element 4 and the inner surface S of the internal flow path R into which it is inserted １ There is no need to worry about liquid-tightness between the fluid and the internal flow path R, and the outer diameter of the fluid resistance element 4 can be designed to be smaller than the flow path diameter of the internal flow path R. This reduces the contact resistance of the fluid resistance element 4 when it is incorporated into the internal flow path R, and prevents the risk of damage.

[0042] Furthermore, since the tapered surface 41 formed at the axial end of the fluid resistance element 4 is in contact with the sealing member 12, the force applied to the fluid resistance element 4 can be distributed in both the axial and radial directions by contact with the sealing member 12, further reducing the risk of damage when incorporated into the internal flow path R.

[0043] The present invention is not limited to the embodiments described above. For example, the fluid resistance element 4 in the above embodiment had tapered surfaces 41 formed at both ends along the axial direction, but this is not the case. In other embodiments of the fluid resistance element 4, the tapered surface 41 may be formed only at one end (for example, the upstream end) of the upstream or downstream side.

[0044] Furthermore, although the fluid resistance element 4 in the above embodiment had only one resistance channel 4r formed therein, it is not limited to this. The fluid resistance element 4 in other embodiments may have multiple resistance channels 4r formed therein.

[0045] In another embodiment, the flow path forming member 1 may be composed of three or more flow path forming blocks 11 that can be divided along the flow direction. For example, as shown in Figure 6, the flow path forming member 1 is located in the upstream region S of the containment space S. Ｕ Upstream block 11 that forms Ｕ and the midstream region S in the containment space S Ｍ midstream block 11 that forms Ｍ and the downstream region S in the containment space S Ｌ downstream block 11 that forms Ｌ It may be composed of the following. In this case, the upstream block 11 Ｕ and downstream block 11 Ｌ The midstream block 11 is made of ceramic material. Ｍ It is preferable that the part is made of a metal material. In this way, the upstream block 11 having a wetted part Ｕ and downstream block 11 Ｌ By using ceramic material, contamination is reduced, and the midstream block 11 does not have wetted parts. Ｍ By constructing it from a metal material, damage to the ceramic fluid resistance element 4 during insertion can be prevented.

[0046] Furthermore, the lengths of each region of the containment space S formed in each of the multiple flow path forming blocks 11 may be the same or different from each other. The lengths of each region of the containment space S may be adjusted as appropriate to facilitate fastening.

[0047] Furthermore, although the fluid resistance element 4 in the above embodiment was entirely made of silicon carbide, it is not limited to this. The fluid resistance element 4 may be made of any corrosion-resistant ceramic material, such as quartz, alumina, zirconia, or silicon nitride. In another embodiment, the flow channel forming member 1 may be entirely made of a metal material.

[0048] The disclosures herein also include fluid control equipment comprising a flow meter 100, a fluid control valve provided upstream or downstream of the flow meter, and a valve controller that controls the opening degree of the fluid control valve based on the deviation between a set flow rate and the flow rate of the fluid output by the flow meter 100.

[0049] Furthermore, the flow meter 100 in the above embodiment is equipped with pressure sensors 2 and 3 attached to the flow path forming member 1, but is not limited thereto. In other embodiments of the flow meter 100, the pressure sensors may not be attached to the flow path forming member 1, and the flow rate may be calculated based on the pressure value on the upstream or downstream side of the fluid resistance element obtained from a pressure sensor provided outside the flow path forming member 1. That is, the disclosure of this specification includes a flow meter that measures the flow rate of a fluid based on the upstream or downstream pressure applied to a fluid resistance element provided in an internal flow path through which the fluid flows, and comprises a flow path forming member that forms the internal flow path, a columnar fluid resistance element made of a ceramic material having a resistance channel fixed to the internal flow path, and a seal member interposed between the wall surface of the internal flow path and the fluid resistance element, wherein the fluid resistance element has a tapered surface formed at its axial end, and the tapered surface is in contact with and fixed to the seal member.

[0050] The present invention can be modified in various ways, as long as it does not contradict its spirit.

[0051] According to the present invention, it is possible to provide a flow meter having a fluid resistance element that can be easily incorporated into a fluid flow path while enjoying the advantages of forming a resistance channel using ceramics, and furthermore, does not cause contamination even when corrosive fluids are flowed through it.

[0052] 100... Flow meter 1... Flow path forming member 11... Flow path forming block 11 Ｕ ...Upstream block 11 Ｌ ...downstream block 11 Ｍ ...Midstream block 12 ...Sealing member, O-ring 2 ...Upstream pressure sensor 3 ...Downstream pressure sensor 4 ...Fluid resistance element 41 ...Tapered surface 42 ...Side surface 4r ...Resistance flow path R ...Internal flow path H １ ...Inflow pipe H ２ ...Outflow piping S ...Containment space S １ ...Inner perimeter wall surface S Ｕ ...Upstream area S Ｌ ...Downstream area S Ｍ ...Midstream region B ...Spatial layer

Claims

1. A flow meter comprising: a flow path forming member that forms an internal flow path through which a fluid flows; a columnar fluid resistance element made of a ceramic material and having a resistance channel fixed to the internal flow path; a pressure sensor that detects the upstream or downstream pressure applied to the fluid resistance element; and a sealing member interposed between the wall surface of the internal flow path and the fluid resistance element, wherein the fluid resistance element has a tapered surface formed at its axial end, and the tapered surface is in contact with and fixed to the sealing member.

2. The flow meter according to claim 1, wherein the flow channel forming member is made of a ceramic material.

3. The flow meter according to claim 1 or 2, wherein the flow path forming member comprises a plurality of flow path forming blocks that are separable from one another, and the housing space in which the fluid resistance element is housed in the internal flow path is divided and formed by the plurality of flow path forming blocks.

4. The flow meter according to claim 3, wherein the flow path forming member comprises, as the plurality of flow path forming blocks, an upstream block that forms an upstream region in the accommodation space and a downstream block that forms a downstream region in the accommodation space, and the fluid resistance element is fixed between the upstream block and the downstream block from both sides along the axial direction.

5. The flow meter according to any one of claims 1 to 4, wherein the fluid resistance element is made of silicon carbide.

6. The flow meter according to any one of claims 1 to 5, wherein the fluid resistance element has a single resistance channel that penetrates in the axial direction.

7. The flow meter according to any one of claims 1 to 6, wherein a space layer is formed between the side surface of the fluid resistance element and the inner wall surface of the internal flow path.

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